In certain prior art, satellite navigation receivers, such as Global Navigation Satellite System (GNSS) receivers, can provide centimeter level estimates of position. Such satellite navigation receivers often rely upon carrier phase measurements that are subject to integer ambiguities of a cycle of the received satellite signal. In some prior art, long initialization periods, also known as pull-in times, are typically 30 to 45 minutes, driven by the time it takes for phase ambiguities to converge to near stable values and for the solution to reach its optimal precision. Prior to the satellite navigation receiver resolving the integer ambiguities of the carrier phase measurements, the precision of the position estimates is degraded.
In some prior art, real-time kinematic (RTK) correction data for the navigation receiver is locally valid, rather than globally valid and requires a significant investment in real-time kinematic base stations and communications links to support communications between a base station and a mobile satellite navigation receiver. RTK navigation applications typically have been restricted to a short range of about 20 kilometers to about 30 kilometers for single baseline between the base station and rover because of distance-dependent biases between the receiver and base station.
In other prior art, Precise Point Positioning (PPP) correction data is globally valid and supports determination of an accurate position solution without regional corrections from additional regional reference stations. However, because PPP correction data only includes the satellite-dependent portion of the measurement errors, prior art PPP methods can take longer time than conventional RTK methods to reach full positioning accuracy.
Under certain circumstances, such as the presence of trees, buildings, obstructions, terrain height changes, fading, or an interfering signal, a GNSS system employing a prior art PPP method may experience a loss or interruption of received (GNSS) satellite signal lock for short time (e.g., for a few minutes) and subsequently regain the signal after the brief loss or interruption. In response to the loss of signal lock and after the interruption, the prior art PPP estimator may reset such that a new convergence period (e.g., at least ten minutes and up to 30 to 45 minutes) is required for the PPP-based-GNSS system to recover back to the full positioning accuracy. Although some prior art attempts to use the last available position estimate prior to loss of lock, the assumption that the last available position estimate did not change materially during the interruption prior can be inaccurate. Accordingly, an operator of heavy equipment, agricultural equipment, construction equipment, forestry equipment or other work vehicle may have significant wasted downtime waiting for the signal to converge, instead of performing work tasks with the work vehicle.
Thus, there is need for a method and satellite receiver system for rapid recovery of precise position after temporary signal loss.